Ejector with gas propulsion

ABSTRACT

Ejector with driver gas comprising at least one primary nozzle branch ( 12 ) with a driver nozzle ( 36 ) having a cross-sectional narrowing and an adjacent receiving nozzle ( 32 ), wherein a suction line ( 24 ) terminates in the narrowing, characterized by at least one connectable secondary nozzle branch ( 14 ) having a driver nozzle ( 38 ) with a cross-sectional narrowing and an adjacent receiving nozzle ( 34 ), wherein the narrowing of the secondary nozzle branch ( 14 ) is connected to a suction line ( 24 ) when the secondary nozzle branch ( 14 ) is opened, and with a closing instrument ( 20 ) connected upstream, with respect to the flow direction of the gas propellant, of the at least one secondary nozzle branch ( 14 ) to connect and disconnect the secondary nozzle branch ( 14 ) in dependence on the inlet pressure of the driver gas entering the ejector ( 20 ).

[0001] This application claims Paris Convention priority of DE 102 50532.2 filed Oct. 29, 2002 the complete disclosure of which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

[0002] The invention concerns a gas driven ejector, i.e. a jet pump, forgenerating underpressure, with at least one primary nozzle branch havinga driver nozzle with a cross-sectional narrowing, an adjacent receivingnozzle, and a suction line connected to the narrowing.

[0003] Conventional ejectors or jet pumps of this type functionaccording to the Venturi principle. The filtered and lubricant-freecompressed gas flows via a connecting sleeve and a pressuring gas feedline into the ejector and reaches the driver nozzle where the flowvelocity of the compressed air serving as the driver gas is increased tosupersonic speed in the narrowing. After exiting the driver nozzle, theair expands and flows into a diffuser and from there, optionally via asound absorber, to the outside thereby producing a vacuum in a chambersurrounding the driver nozzle with air being pumped via a suction linefeeding into the chamber. The pumped air and the driver gas introducedinto the ejector both exit the ejector via the expansion section.

[0004] With respect to other vacuum pumps, these jet vacuum pumpsadvantageously have no rotating parts and maintenance and wear aretherefore minimum. Moreover, they cannot explode since they functionpurely pneumatically. In addition, their construction is simple and theycan be installed at any location. They do not generate heat and can beconnected and disconnected at any time to save energy. Moreover, thevacuum can be generated quickly using short lines between e.g. a suctiongripper and the ejector. The compact construction, the low weight andthe ability to combine several functions in one device play an importanteconomic role in the field of construction, work preparation,purchasing, mechanical processing, assembly, putting into operation andspare part supply.

[0005] In view of the above, it is the underlying purpose of theinvention to provide a gas propulsion ejector which ensures good suctionperformance in a straightforward manner with low driver gas consumption.

SUMMARY OF THE INVENTION

[0006] This object is achieved in accordance with the invention in thatat least one connectable secondary nozzle branch is provided which has adriver nozzle with a narrowing and an adjacent receiving nozzle, whereinthe narrowing of the secondary nozzle branch is connected to a suctionline when the nozzle branch is connected, with a closing instrumentbeing disposed upstream of the at least one secondary nozzle branch toconnect/disconnect the secondary nozzle branch in dependence on theinput pressure of the driver gas in the ejector.

[0007] In accordance with an embodiment of the invention, the secondnozzle branch, e.g. the secondary nozzle branch, is only connected whenthe inlet pressure is high. The second Venturi nozzle is then activatedto provide a very high suction capacity and associated high vacuum. Inthis case, both Venturi nozzle suction capacities are combined toevacuate e.g. the feed line to a suction gripper. Since the secondVenturi nozzle is connected only when required, no driver gas is wasted.In this fashion, the modular connection of one or more additionalVenturi nozzles individually adjusts the suction performance whileproviding sufficient flow velocity at high as well as low requiredsuction performance to always ensure safe operation of the evacuationprocess.

[0008] Alternatively, the secondary nozzle branch may be connected whenthe inlet pressure is below a certain switching pressure. In this case,both nozzle branches are used only when the inlet pressures are low andevacuation takes place only via one nozzle branch, i.e. the primarynozzle branch when the inlet pressure is high.

[0009] In accordance with an embodiment, the closing instrument may beheld in a first position via a preloading force which counteracts theinlet pressure of the driver gas. The closing instrument may e.g. be abistable 2/2 way valve. In this case, the preloading force is providedby a spring which acts e.g. on a piston. Depending on whether thesecondary nozzle branch is to be connected at low or high workingpressures, the first position is defined as the open or closed position.The stop valve or closing instrument is adapted to the desired switchingdirection. When the switching pressure is reached, the inlet pressurecan switch the closing instrument into a second position with thatsecond position being either that state of the closing instrument withwhich the secondary branch contributes to the suction performance orthat state in which it is disconnected, in dependence on the desiredswitching direction.

[0010] The two nozzle branches may also have a common feed line whichcontains the closing instrument. In most cases, the driver gas ispressurized air.

[0011] According to a further embodiment, the primary and the secondarynozzle branch may have a common suction line which may, in particular,be a continuous suction line which communicates with the two nozzlebranches. A check valve may be disposed in the suction line between thesecondary and primary nozzle branch to prevent leaking of the vacuumgenerated by the first nozzle branch when the secondary nozzle branch isdisconnected. When an underpressure is also generated in the secondarynozzle branch, the check valve opens and the underpressure of thesecondary nozzle branch also contributes to the suction performance inthe suction line.

[0012] Alternatively, at least the secondary nozzle branch, a furthernozzle branch, or a group of nozzle branches may each have its ownseparate suction line. Towards this end, several suction circuits may beconnected or disconnected independently of each other.

[0013] The check valve may preferably be a spring-loaded ball valve. Thespring forces may be adjusted such that even a small force is sufficientto overcome the spring. In this case, the check valve may already liftoff during low suction performance of the secondary nozzle branch. Thelow spring force is sufficient, since the stop ball is additionallypressed against the closure seat by the underpressure generated when thefirst nozzle branch is operated to thereby safely prevent leakage. Ifthe spring has a low spring constant, two nozzle branches of equalsuction performance may also be operated, since, in this case, theclosing element is in a bistable state and the suction line is openedfor the second nozzle branch.

[0014] The secondary nozzle branch may have the same or a differentsuction performance than the primary nozzle branch and preferably ahigher suction performance, since this ensures complete and simpleopening of the check valve. By providing different Venturi nozzles ofdifferent types or performance classes, the suction performance effectedin the suction line and exhaust connection may be varied to permitreliable adjustment of the required underpressure and evacuation time.

[0015] In addition to the above-described two nozzle branches, severalprimary and secondary nozzle branches, which are connected in parallel,may also be provided, with all primary nozzle branches being connectedat the same time and all secondary nozzle branches being connected ordisconnected at a common switching pressure. In addition to thesecondary nozzle branch, a tertiary or quaternary nozzle branch may beprovided which is disconnected or connected at a further switchingpressure other than the first switching pressure, to further improve theregulation and control of the suction performance in accordance with therequirements.

[0016] All nozzle branches may be connected to one single suction line,preferably in that the nozzle branches intersect that suction line.

[0017] The check valves may be preferably provided only between branchesof different connection pressures. In this manner, no check valves areprovided between different primary nozzle branches and only one checkvalve is provided between a group of primary nozzle branches and a groupof secondary nozzle branches. If, in addition to primary and secondarynozzle branches, tertiary nozzle branches are also provided, a checkvalve may be disposed between the primary and the secondary and tertiarynozzle branches.

[0018] All components and nozzle branches of the ejector can thereby bedisposed within a common housing. The housing may consist e.g. of amaterial block into which all lines are introduced as bores with thenozzles and valves being inserted into the block and fixed therein withremaining openings being closed by caps. This provides particularadvantages for maintenance, configuration, and replacement of individualcomponents.

[0019] Further advantages and features of the invention can be extractedfrom the disclosure. The drawing gives a detailed description of aparticularly preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWING

[0020]FIG. 1 shows a diagram of connections of an inventive ejector;

[0021]FIG. 2 shows an exploded view of an inventive ejector; and

[0022]FIG. 3 shows a section through an inventive ejector.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0023]FIG. 1 shows a circuit diagram of an ejector or jet pump,designated in its entirety with 10. The ejector 10 has a primary nozzlebranch 12 and a secondary nozzle branch 14. The two nozzle branches areconnected to a feed line 16 for a driver gas, wherein in FIG. 1, acommon air supply branch 16 branches into the air supply branches 16′and 16″ for the primary nozzle branch 12 and the secondary nozzle branch14, respectively. The air supply branch 16′ for the primary nozzlebranch supplies driver gas to a first Venturi arrangement 18 of thefirst supply branch 12. A switching valve 20 is disposed in the secondair supply branch 16″ to pass air to the second Venturi arrangement 22of the second nozzle branch 14 or to close off the air supply line 16″of the second arrangement 22.

[0024] The valve 20 is a bistable 2/2 way valve and is explained in moredetail below.

[0025] The primary nozzle branch 12 and the secondary nozzle branch 14are connected to a suction line 24. One single suction line 24 connectsto the two nozzle branches 12, 14 in the region of their respectivecross-sectional narrowings of the Venturi arrangements 18, 22. A furtherline, e.g. for a suction gripper, may be evacuated via the suction line24 which feeds to a suction nozzle 26. A check valve 28 (a spring-loadedball valve) is disposed in the suction line 24 between the primarynozzle branch 12 and the secondary nozzle branch 14 to prevent leakageof the vacuum of the first nozzle branch 12 in the event that thesecondary nozzle branch is not connected.

[0026] In the circuit of FIG. 1, the ejector 10 is operated only withrespect to the primary nozzle branch 12 as soon as it is loaded withdriver gas (compressed air). The valve 20 is thereby held in theblocking position. Acceleration of the compressed air to supersonicspeed in the primary nozzle branch 12 generates an underpressure in theregion of its cross-sectional narrowing in a chamber surrounding thenarrowing, through which the suction line 24 is evacuated. The checkvalve 28 prevents leakage of vacuum in the chamber.

[0027] As soon as the supply pressure in the feed line 16 of thecompressed air reaches a predetermined switching pressure for the valve20, the second, i.e. secondary nozzle branch 14 is opened. At thismoment, the air consumption is doubled, as is the suction volume.

[0028] As soon as the inlet pressure is reduced, the valve 20 switchesback to the blocked position.

[0029] A certain switching hysteresis of the valve 20 must thereby betaken into account.

[0030] The switching pressure is thereby predetermined by the valve 20.

[0031] The structure is explained below using an exploded view of aninventive ejector 10. The ejector 10 is mounted in a housing 29 and canbe fixed through the housing 29 to a base e.g. via mounting locations30.

[0032] The two nozzle branches 12 and 14 thereby consist essentially ofa receiver nozzle 32 or 34 and a driver nozzle 36 or 38, which areconnected to each other via an O-ring 40 and form the Venturiarrangements 18, 22. The cross-sectional narrowing in the driver nozzle36 or 38 accelerates the compressed air introduced into the feed line 16to supersonic speed.

[0033] A check valve 28 comprising a ball 42 as the closing body and aspring 44 with a low spring constant is disposed between the two nozzlebranches 12 and 14 in the suction line 24 which connects the two nozzlebranches 12 and 14 and which feeds to a suction nozzle 26. The vacuumgenerated in the primary nozzle branch 12 is thereby protected fromleakage with respect to the secondary nozzle branch.

[0034] The suction line 24 is closed on both sides of the housing 29through which it penetrates using cover flaps 46, in particular plasticlids.

[0035] In a particularly simple fashion, the housing 29 is not merely acover for the individual parts but a material block into which theindividual recesses for the feed line etc. such as e.g. the suction lineand the compressed air lines of the nozzle branches 12, 14, whichintersect the suction line, are machined, wherein only components suchas the driver nozzle, the receiving nozzle, and the valves are separateand are inserted into and fixed in the housing block. In this fashion,replacement of the individual component or insert is particularly easy.A jet pump 10 of this type can be easily adjusted to different types orperformance classes without having to replace the entire jet pump 10.For cleaning and/or inspection, the individual nozzles 32-38 can beeasily removed, cleaned or examined and be subsequently re-installed.Faulty individual parts may be particularly easy to replace.

[0036] A 2/2 way valve 20 may be provided in the region of the feed linewhich comprises a piston 48 which forms a unit together with a pistonseal 50 and an O-ring seal 52. The piston is pressed by a spring 54 inthe direction of its longitudinal axis, whose spring constant and biaspermits adjustment of the switching point. The O-ring 52 thereby sealsthe compressed air line of the secondary nozzle branch 14 when thepiston 48 is in a closed position, i.e. in its first or restingposition.

[0037] The side of the spring 54 facing away from the piston 48 abuts aplug 56 via which the spring bias can be adjusted.

[0038] When the valve 20 is closed, compressed air for the primarynozzle branch 12 can flow unhindered past the switching piston 48. Theswitching piston has different cross-sections along its length, with thepressure of the flowing compressed air acting on the piston 48, via anannular surface of larger cross-section formed at a front side of thepiston 48 in the region of the larger cross-section to oppose theloading direction of the spring 54. The compressive forces of thepressurized air thereby depend on the circular area 51 of the piston 48at which those forces act as well as on the absolute pressure.

[0039] The smaller cross-sectional surface of the piston 48 whichcorresponds to a corresponding smaller bore in the housing 28 is therebydisposed in the direction of the second 14 nozzle branch.

[0040] If there is compressed air in the feed line 16, the piston 48 isloaded with pressure at its surface 51. This force acts against the biasof the spring 54. As the pressure is increased and as soon as the forceexerted by the compressed air exceeds the spring force, the piston 48 ismoved against the spring force in the direction of the plug and up to apredetermined stop. The feed line to the secondary nozzle branch 14 isthereby opened and the secondary nozzle branch contributes to thesuction performance. This doubles the air consumption and the suctionvolume.

[0041] If the supply pressure on the inlet line 16 is reduced, thepiston 48 moves back towards the second nozzle branch 14 until theO-ring 52 of the piston seal 50, piston 48 and O-ring 52 assembly abutsthe corresponding bore 53 and the associated surface in the housingblock 29 to seal the piston 48 in the position on the conical surface53.

[0042]FIG. 3 shows the ejector 10 of FIG. 2 in an assembled stateillustrating the position of the check valve between the nozzle branches12 and 14.

[0043] The pressure forces of the compressed air thereby act on theannular surface 51. The spring force of the spring 54 opposes thesepressure forces produced by compressed air. If the pressure forcesexceed a switching pressure, the piston 48 is pressed downwards (in theillustration) against the spring 54 and permits passage of compressedair to the second nozzle branch 14.

[0044] As soon as the second nozzle branch also produces a vacuum, theball 42 of the check valve is moved against the spring force of thespring 44 by the vacuum in the second nozzle branch 14 and towards thesecond nozzle branch 14 to open the passage in the suction line 24,wherein additional vacuum is generated on the suction nozzle 26, e.g.for a suction gripper. The suction performance of the secondary nozzlebranch 14 must be greater than or equal to that of the primary branch 12in order to hold the check valve 28 in the open position.

[0045] As soon as the pressure in the feed line 16 decreases, and thepiston 48 closes the feed line to the second nozzle branch 14, the ball42 is pressed back into its valve seat by the force of the spring 44 toclose the suction line 24 in the region of the narrowing of the firstnozzle branch 12, thereby preventing leakage.

[0046] In this fashion, a second nozzle branch 14 can be connected onlywhen increased suction performance is required and in all other cases,air consumption can be reduced. The air consumption and suctionperformance can thereby be efficiently controlled.

We claim:
 1. An ejector having a driver gas at an inlet pressure, the ejector comprising: at least one primary branch; a primary driver nozzle disposed within said primary branch, said primary driver nozzle having a primary driver cross-sectional narrowing; a primary receiver nozzle disposed downstream of and adjacent to said primary driver nozzle; a primary suction line in vacuum communication with said primary driver narrowing; at least one secondary branch; a secondary driver nozzle disposed within said secondary branch, said secondary driver nozzle having a secondary driver cross-sectional narrowing; a secondary receiver nozzle disposed downstream of and adjacent to said secondary driver nozzle; a secondary suction line in interruptable vacuum communication with said secondary driver narrowing; and a closing instrument disposed upstream of said secondary driver nozzle to connect and disconnect said secondary branch in dependence on the inlet pressure of the driver gas into the ejector.
 2. The ejector of claim 1, wherein said closing instrument is held in a first position through a biasing force means, said biasing force means counteracting the inlet pressure of the driver gas.
 3. The ejector of claim 2, wherein said closing instrument comprises a piston.
 4. The ejector of claim 3, wherein said biasing force means comprises a spring which acts on said piston.
 5. The ejector of claim 1, wherein said closing instrument is transferred to a second position when a switching pressure is reached by the inlet pressure of the driver gas.
 6. The ejector of claim 5, wherein said at least one secondary branch is disconnected when the inlet pressure is lower than said switching pressure.
 7. The ejector of claim 5, wherein said at least one secondary branch is disconnected when the inlet pressure is higher than said switching pressure.
 8. The ejector of claim 1, further comprising a common driver gas feed line communicating with said primary and said secondary branches, wherein said closing instrument is disposed in said feed line.
 9. The ejector of claim 1, wherein said primary suction line and said secondary suction line coincide, and further comprising a check valve disposed in said primary and secondary suction line between said secondary branch and said primary branch to prevent leakage of vacuum generated by said primary branch when said secondary branch is disconnected.
 10. The ejector of claim 1, wherein each nozzle branch or each group of nozzle branches is/are associated with a separate suction line.
 11. The ejector of claim 9, wherein said check valve is a spring-loaded ball valve.
 12. The ejector of claim 1, wherein said secondary branch has a same suction performance as said primary branch.
 13. The ejector of claim 1, wherein said secondary branch has a different suction performance than said primary branch.
 14. The ejector of claim 13, wherein said secondary branch has a larger suction performance than said primary branch.
 15. The ejector of claim 1, further comprising a housing, wherein suction lines are bores in said housing and nozzles and valves are disposed in said housing in an exchangeable manner. 